Permanently excited synchronous motors are described in U.S. Pat. No. 5,642,013. In addition to a particular ratio between the spacing of the teeth of the primary component and the spacing of the magnets of the secondary component that leads to a reduced cogging torque, the straight tooth flanks, in particular, are considered advantageous. They make it possible to slip the coils of the primary component in prefabricated form onto the individual teeth of the primary component. In so doing, attention should be paid to satisfactory insulation of the coils from the teeth of the iron core and from the air gap of the motor.
It is conventional to line the teeth gaps (i.e., the grooves of the iron core) with insulating paper or to wind such paper around the straight regions of the coils. The end windings of the coils laterally projecting from the iron core are sheathed in a casting compound (synthetic resin) for mechanical stabilization and electrical insulation. It is also conventional to press an elastic spacer having a tapering free end into the opening that is formed by an end winding and a tooth, which not only imparts additional mechanical stability to the end winding, but also provides electrical insulation between the end winding and tooth. This is of particular importance in this region, because it is quite difficult to insert insulating paper into the curved region of the coil. Using such spacers at both opposite end windings of a coil also centers and fixates the coil around the tooth.
To improve the insulation of the end windings from the air gap of the motor, it is conventional to place a sheet of insulating material in front of the end windings, which subsequently is encapsulated in resin together with the end windings.
The production process for such a motor and in particular the mechanical stabilization and electrical insulation of the end windings thus is relatively complex.